Many attempts have been made to provide a bentonite composition having sufficient cohesiveness and structural integrity to provide a modeling clay-like or putty-like consistency. Such bentonite compositions can be in a paste or putty-like form for handleability so that a desired quantity can be applied in a selected location for water seepage control. A major problem associated with attempting to provide a bentonite composition with a paste or putty-like consistency in order to provide the desired handleability is that many additives used to provide such consistency interfere with the swelling capacity of the bentonite. One attempt to provide a bentonite composition with a putty-like consistency is described in the Bechtner U.S. Pat. No. 2,277,286 wherein water is added to the bentonite to hydrate a portion of the bentonite to achieve the desired consistency. The resulting composition is a putty-like mass which is sufficiently cohesive as a result of the partial swelling of the bentonite, but the swellability of the bentonite is substantially retarded since only about 70-80% of its potential absorbing and swelling characteristics are retained. Further, the Bechtner mass will only adhere to surfaces so long as it remains moist.
Other attempts have been made to provide a bentonite composition having a handleable consistency such as in a paste-like or putty-like form while retaining the full swelling properties of the bentonite by the addition of non-aqueous liquids, such as set forth in this assignee's prior U.S. Pat. No. 4,279,547 and the McGroarty U.S. Pat. No. 4,316,833. Generally, the addition of liquid organic additives to bentonite will inhibit the swelling capacity of the bentonite to various degrees depending on the characteristics of the organic additive, and most notably dependent upon the polarity of the organic additive. In accordance with the McGroarty U.S. Pat. No. 4,316,833, an attempt is made to provide a cohesive bentonite composition having a paste-like consistency without hydrating the bentonite by the addition of adhesive agents, such as hydrocarbon resins. In accordance with the McGroarty U.S. Pat. No. 4,316,833 "if the adhesive penetrates the bentonite, it will destroy the ability of the bentonite to swell and thus will destroy its waterproofing capabilities". In an attempt to prevent the adhesive agent penetration, the McGroarty bentonite is first saturated with a liquid fluidizer, such as mineral spirits, to prevent the adhesive agent from substantially penetrating the bentonite particles after saturation with the liquid fluidizer.
This assignee's prior U.S. Pat. Nos. 4,209,568 and 4,279,547 describe other attempts to provide a bentonite composition having a consistency for good handleability such as a stiff putty-like consistency without hydrating the bentonite and without saturation of the bentonite with bentonite-inhibiting organics by forming a gel and adding the bentonite to the gel to prevent bentonite saturation while maintaining its swellability.
The Ishido U.S. Pat. No. 4,366,284 discloses a bentonite composition having 10-40% rubber, 10-40% plasticizer and 10-20% silicic filler. The silicic filler in an amount of at least 10% by weight is disclosed to be critical for swellability. In accordance with one embodiment of the present invention, it has been found that the compositions of the present invention achieve substantially increased swellability so long as the composition contains essentially no silicic filler.
It has been found that the composition set forth in this assignee's prior U.S. Pat. No. 4,279,547 and in the McGroarty U.S. Pat. No. 4,316,833, while generally satisfactory in terms of composition consistency and maintenance of swellability, inhibit the swelling of the bentonite to a limited extent. A number of patents disclose the use of a liquid impermeable liner of polymeric sheet material, bentonite clay, or layers of the two to prevent escape of liquid or liquid waste materials to the surrounding environment. Examples of such patents include Wright U.S. Pat. No. 4,255,067; Draper et al. U.S. Pat. No. 4,035,543; and Blais U.S. Pat. No. 4,344,722.
Other patents disclose the use of various plastic sheet or resin materials as water-proofing layers: Ionides U.S. Pat. No. 3,234,741; Stapelfeld U.S. Pat. No. 3,326,001; Berry U.S. Pat. No. 3,383,863; Schaefer et al. U.S. Pat. No. 3,415,022; and Draper et al. U.S. Pat. No. 3,474,625. The following patents disclose the use of asphalt or other bituminous material together with other materials, reinforcements or liners for lining earthen formations: VanHulst U.S. Pat. No. 2,190,003; Bramble U.S. Pat. No. 2,771,745; Cash et al. U.S. Pat. No. 3,160,512; and Rossi U.S. Pat. No. 3,380,254. The VanHulst U.S. Pat. No. 2,190,003 discloses the combination of bituminous substances and clay for admixture with soil.
In accordance with the present invention, it has been found that bentonite intimately admixed with polypropene, polybutene, or mixtures thereof will form a bentonite composition having a paste-like or putty-like consistency; sufficient tack to be adhered to a wall, floor, roof, conduit and the like; and most suprisingly and unexpectedly will increase the swelling capacity of the bentonite. In accordance with another embodiment of the present invention, a cohesive bentonite composition includes bentonite, an elastomer, and a plasticizer compatible with the elastomer. The compositions of the present invention readily adhere to a layer of flexible sheet material to provide a composite sheet material laminate. When adhered to a water-impermeable sheet layer, any holes or cracks formed in the sheet material layer when the composite material is applied, or during aging, will be self-healed upon contact of water on the bentonite composition immediately below the hole or crack to prevent water seepage through the composite sheet material.